1. Field of the Invention
This specification teaches a new method for disinfecting and sterilizing air, surfaces of all types and food from microorganisms and toxic chemical substances. In addition, it relates to a process and apparatus for protecting surfaces in closed or captured environments (zones) from external sources of microbial contamination in an efficient and cost effective process. These zones can be large volumes such as high rise building, cruise ships and jet airliners, or small volumes such as small rooms or surgical operation areas whether in a hospital operating room or on the battle field.
2. Description of the Related Art
All prior art for sterilizing and disinfecting air has been based on using commercially available ultra-violet (UV) lamps or by using magnetic fields. These lamps are either pulsed or continuous. Continuous lamps are mercury based and emit principally at 254 nm. A number of companies are presently producing UV light based apparatus for the destruction of “virus, bacteria, spores and pathogens” (microorganisms or VSP) that are in room air. This is an effective treatment because it continually exposes room air currents to the treatment light and over time has sufficient exposure time to treat VSP's. The required exposure times range from 10's to 100's of seconds, depending on the light absorption capability of the different virus and bacteria at the 254 nm. While this is effective for treating the room air of individual rooms, it requires a long time to be effective in treating large flowing volumes of air that pass quickly down large ducts. Its long treatment time is impractical for treating most surfaces.
Magnetic based apparatus also require time to deactivate or destroy these VSP's. Two such inventions are directed to specific applications. Wesley, U.S. Pat. No. 4,458,153 is directed specifically towards liquid like substances enclosed in pipes, but does not discuss any test results. Sangster, U.S. Pat. No. 5,750,072 requires an injection of a sterilizing fluid as a mist or vapor for the magnetic field to produce radicals that in turn are used to alter the VSP's. He does not discuss any test results. Hofmann, U.S. Pat. No. 4,524,079 is directed specifically to treating food stuffs. He speaks of requiring up to 100 pulses at frequencies ranging from 5 to 500 kHz. Although the action time would be short, the power required to treat large areas and the apparatus design limit its practical application. None of these patents are admitted to being prior art by their mention in this background section.
The broad ultraviolet spectrum had been divided into three regions depending on its different effects on human skin. Reference to these regions are predominantly made in medical terminology with UV-A defined as a range or band between 320 nm and 400 nm, UV-B defined as a band between 280 nm and 320 nm, and UV-C defined as encompassing wavelengths shorter than 280 nm. Recently the UV-C band has been shortened because strong water absorption causes different effects on the skin below 235 nm. UV-C is now considered the band encompassing wavelengths from 280 nm to 235 nm. The Far UV begins at 235 nm and encompasses wavelengths to the beginning of vacuum UV at 185 nm. Photochemists and photobiologists do not generally use these terms because absorption spectra of chemical bonds are much narrower than these generally defined bands. Instead, they use the wavelength of the applied radiation to define the observed effects.
Claims have been made that UV-C radiation is used to alter the DNA. This is because the mercury lamp emission at 254 nm is close to a good DNA absorption band and is the most widely available UV-C radiation source. None of these claims make reference to any shorter wavelengths and to the absorption band that peaks at 200 nm (see FIG. 9). Most literature credits this peak to protein absorption whereas the peak centered near 260 nm is attributed to many amino acids. In fact, all literature directs researchers away from using any shorter wavelengths due to the high absorption of molecular water. Mercury lamps are used for wastewater treatment and work well for this application. However, this specification teaches that since we do not live underwater, the protein absorption band offers much more significant action spectra that can be used to alter the DNA of microorganisms more effectively. A source of Far UV photons targets this protein absorption band. This concept is a significant advancement and a step change in the technology used for sterilization and disinfection.
During the past few years, new UV emitting lamps based on the excitation of excimers are becoming commercially available. These emitters produce single line or narrow spectral emission at a wavelength determined by the gas composition of the lamp. If the treatment lamp's wavelength is chosen to match closely to the peak of protein absorption of the microorganism's DNA, then a lethal dosage can be delivered to the VSP's in a shorter time. No patent has been found that teaches the use of “new ultra-violet” (NUV) sources coupled with supporting equipment that can effectively and efficiently disinfect and sterilize large volumes of air, large and small surfaces, and food stuffs in various stages of preparation in a practical manner.
The NUV lamp is a coaxial design that can be made as small as a pencil to as large as 1 meter long. Lamp efficiency is about 10-25% wall power to UV emission. The design has several advantages over mercury lamps. Most important is that its gas can be chosen to maximize its emission to the absorption peak of the targeted biochemical. Unlike the mercury lamp, the UV intensity can be varied from near zero to maximum. It will produce 10 to 1000 times more intensity than mercury, depending on the lamp dimensions, and it does not use mercury that will soon become regulated by the EPA.
In this specification, sterilization or sterilize refers to sterilization or high level disinfectant as defined by US FDA. The terms disinfectant and disinfection refers to all other levels of disinfection.